Re: [linux-next:master] [mm] 0fa2857d23: WARNING:at_mm/page_alloc.c:#__alloc_pages_noprof

[Matthew Wilcox]

On Mon, Jun 24, 2024 at 11:53:30AM -0700, Yosry Ahmed wrote:
> After a page is swapped out during reclaim, __remove_mapping() will
> call __delete_from_swap_cache() to replace the swap cache entry with a
> shadow entry (which is an xa_value).

Special entries are disjoint from shadow entries.  Shadow entries have
the last two bits as 01 or 11 (are congruent to 1 or 3 modulo 4).
Special entries have values below 4096 which end in 10 (are congruent
to 2 modulo 4).